I believe there is an error in attack protocal when fleets have matching contents.
To my understanding, the last fleet takes all overage in enemy attack when the number of fleets do not match up.
I have now lost 2 ships to this issue today.

Invader NightScourge (#76230)
Engaged Units
Fleet Name # of Units Attack Defence Hitpoints
CrimsonScourge E6 1 370.872.466+ 0+ 426.137.026
CrimsonScourge E6 1 370.872.466+ 0+ 426.137.026
Defender Unidentified Fleet (#)
Engaged Units
Fleet Name # of Units Attack Defence Hitpoints
The Hellish Disgrace MK 5 25.327 166.686+ 0+ 10.382
Semakaramon MK 12 33.897 66.247+ 0+ 6.349
Gecko Elemental MK 7 34.288 78.082+ 0+ 23.179
Demon Scions From D'ulzsa MK 8 28.480 55.882+ 0+ 5.542
Our long range scanners report 35,659,135 enemy fleet power!
Engage
Assault Note
NightScourge(#76230)'s CrimsonScourge E6 fleet engaged Unidentified Fleet(#)'s The Hellish Disgrace MK 5 fleet on the battlefield.
The fleet CrimsonScourge E6 did 250.338.915 damage to fleet The Hellish Disgrace MK 5.
NightScourge(#76230)'s CrimsonScourge E6 fleet destroyed 24.112 of Unidentified Fleet(#)'s The Hellish Disgrace MK 5 fleet.
The fleet The Hellish Disgrace MK 5 did 189.974.534 damage to fleet CrimsonScourge E6.
Unidentified Fleet(#)'s The Hellish Disgrace MK 5 attack failed.
NightScourge(#76230)'s CrimsonScourge E6 fleet engaged Unidentified Fleet(#)'s Semakaramon MK 12 fleet on the battlefield.
The fleet CrimsonScourge E6 did 215.212.053 damage to fleet Semakaramon MK 12.
NightScourge(#76230)'s CrimsonScourge E6 fleet destroyed 33.897 of Unidentified Fleet(#)'s Semakaramon MK 12 fleet.
The fleet Semakaramon MK 12 did 181.891.539 damage to fleet CrimsonScourge E6.
Unidentified Fleet(#)'s Semakaramon MK 12 attack failed.
Unidentified Fleet(#)'s Gecko Elemental MK 7 fleet attacks NightScourge(#76230)'s CrimsonScourge E6 fleet.
The fleet Gecko Elemental MK 7 did 156.620.623 damage to fleet CrimsonScourge E6.
Unidentified Fleet(#)'s Gecko Elemental MK 7 attack failed.
The fleet CrimsonScourge E6 did 38.941.609 damage to fleet Gecko Elemental MK 7.
NightScourge(#76230)'s CrimsonScourge E6 fleet destroyed 1.680 of Unidentified Fleet(#)'s Gecko Elemental MK 7 fleet.
Unidentified Fleet(#)'s Demon Scions From D'ulzsa MK 8 fleet attacks NightScourge(#76230)'s CrimsonScourge E6 fleet.
The fleet Demon Scions From D'ulzsa MK 8 did 79.541.869 damage to fleet CrimsonScourge E6.
Unidentified Fleet(#)'s Demon Scions From D'ulzsa MK 8 fleet destroyed 1 of NightScourge(#76230)'s CrimsonScourge E6 fleet.
The fleet CrimsonScourge E6 did 0 damage to fleet Demon Scions From D'ulzsa MK 8.
NightScourge(#76230)'s CrimsonScourge E6 attack failed.
Assault result
NightScourge(#76230)'s 1 / 1 (100%) CrimsonScourge E6 are destroyed during battle.
Unidentified Fleet(#0)'s 24112 The Hellish Disgrace MK 5 are destroyed during battle.
Unidentified Fleet(#0)'s 33897 Semakaramon MK 12 are destroyed during battle.
Unidentified Fleet(#0)'s 1680 Gecko Elemental MK 7 are destroyed during battle.
You attacked Unidentified Fleet(#0)'s fleet and mothership from deep space.
You destroyed Unidentified Fleet(#0)'s 59689 ships and lost 1/2 ships.
You lost 15.880.047/31.760.094 fleet power (50%), while the enemy lost 17.839.135/35.659.135 fleet power (50%)
Primary Objective: Destroy 32% of the enemy while losing less percent of the armada then the enemy.
Your attack failed and achieved nothing.
You lost more power than Unidentified Fleet(#0) during battle.
Mathematically, the enemy damage would have come up 8,082,995 short of destroying the tail fleet. Although, matching the overage to the first fleet would've produced a confirmed destruction of the fleet.
I would appreciate any assistance in this matter.